1. Field of Invention
The device described herein relates generally to the production of oil and gas. More specifically, the device described herein relates to a running tool with an off center attachment compensating for asymmetric christmas trees.
2. Description of Related Art
Subsea wellhead assemblies are typically used in the production of hydrocarbons extracted from subterranean formations below the seafloor. Subsea wellhead assemblies generally comprise a wellhead housing attached at a wellbore opening, where the wellbore extends through one or more hydrocarbon producing formations. Casing and tubing hangers are landed within the housing for supporting casing and production tubing inserted into the wellbore. The casing lines the wellbore, thereby isolating the wellbore from the surrounding formation. Tubing typically lies concentric within the casing and provides a conduit for producing the hydrocarbons entrained within the formation. Wellhead assemblies also typically include christmas trees connecting to the upper end of the wellhead housing. The christmas trees control and distribute the fluids produced from the wellbore.
The christmas trees are installed onto the wellhead housing by latching a running tool within the tree's main annulus and attaching wire or drill pipe to the running tool for lowering subsea to the wellhead housing. Often the tree's center of gravity is not coincident with the annulus axis; which if uncorrected causes the tree to tilt to prevent properly landing the tree onto the wellhead housing. The asymmetric tree can be balanced with added weights, but weight balancing is limited by the lowering wire and drill pipe structural limits. Additionally, christmas trees are becoming more complex and heavier thereby making weight balancing less desirable. This is exacerbated by subsea well operator using older rigs to install the newer larger and heavier tree systems. As a result the rigs experience difficulty while transferring the trees from supply vessels to the rig.